U.S. patent number 6,625,973 [Application Number 10/081,131] was granted by the patent office on 2003-09-30 for lock mechanism.
This patent grant is currently assigned to Lucas Industries Limited. Invention is credited to Melanie Zoe Brown, John Herbert Harvey, Tony Jones, David John Langford, Michael Paul Somerfield.
United States Patent |
6,625,973 |
Langford , et al. |
September 30, 2003 |
Lock mechanism
Abstract
A thrust reverser actuator lock mechanism comprising a rotatable
shaft, rotation of which in one direction from a rest position
drives an associated thrust reverser from a stowed position towards
an operative position in use, retractable abutment means having a
rest position abutting an element rotatable with the shaft to
prevent rotation of the shaft, resilient means urging said abutment
means to said rest position, and, mechanical latch means sensitive
to the speed of rotation of said shaft for latching said abutment
means in a retracted position against the action of said resilient
means when the rotational speed of said shaft exceeds a
predetermined value.
Inventors: |
Langford; David John
(Wolverhampton, GB), Harvey; John Herbert
(Wolverhampton, GB), Jones; Tony (Birmingham,
GB), Somerfield; Michael Paul (Stoke-on-Trent,
GB), Brown; Melanie Zoe (Wolverhampton,
GB) |
Assignee: |
Lucas Industries Limited
(GB)
|
Family
ID: |
26245753 |
Appl.
No.: |
10/081,131 |
Filed: |
February 22, 2002 |
Foreign Application Priority Data
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Mar 21, 2001 [GB] |
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0107023 |
Feb 23, 2001 [GB] |
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0104565 |
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Current U.S.
Class: |
60/226.2;
292/207; 60/39.091 |
Current CPC
Class: |
F02K
1/766 (20130101); F15B 15/261 (20130101); Y10T
292/1089 (20150401) |
Current International
Class: |
F15B
15/26 (20060101); F15B 15/00 (20060101); F02K
1/76 (20060101); F02K 1/00 (20060101); F02K
003/02 () |
Field of
Search: |
;6/226.2,230,39.091
;292/207 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 536 954 |
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Apr 1993 |
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EP |
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0 801 221 |
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Oct 1997 |
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EP |
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2 706 536 |
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Dec 1994 |
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FR |
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0 506 277 |
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Mar 1992 |
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GB |
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0 801 221 |
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Oct 1997 |
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GB |
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1 236 881 |
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Sep 2002 |
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GB |
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Primary Examiner: Freay; Charles G.
Assistant Examiner: Liu; Han L
Attorney, Agent or Firm: Andrus, Sceales, Starke &
Sawall
Claims
What is claimed is:
1. A thrust reverser actuator lock mechanism comprising a rotatable
shaft, rotation of which in one direction from a rest position
drives an associated thrust reverser from a stowed position towards
an operative position in use, retractable abutment means having a
rest position abutting an element rotatable with the shaft to
prevent rotation of the shaft, resilient means urging said abutment
means to said position, and, mechanical latch means sensitive to
the speed of rotation of said shaft for latching said abutment
means in a retracted position against the action of said resilient
means when the rotational speed of said shaft exceeds a
predetermined value.
2. A thrust reverser actuator lock mechanism as claimed in claim 1
wherein said mechanical latch means co-operates with said abutment
means in such a manner that when said latch means latches said
abutment means in said retracted position the abutment means must
be retracted beyond said latched position and the speed of rotation
of the shaft must be below said predetermined value in order for
the latch means to cease to be operative so that the abutment means
can move to its rest position.
3. A thrust reverser actuator lock mechanism as claimed in claim 1
including electromagnetic retraction means for retracting said
abutment means from said rest position.
4. A thrust reverser actuator lock mechanism as claimed in claim 1
including hydraulic retraction means for retracting said abutment
means from said rest position.
5. A thrust reverser actuator lock mechanism comprising a rotatable
shaft, rotation of which in one direction from a rest position
drives an associated thrust reverser from a stowed position towards
an operative position in use, at least one retractable abutment
having a rest position abutting an element rotatable with the shaft
to prevent rotation of the shaft, at least one resilient component
urging said at least one abutment to said rest position, an
electromagnetically actuated retractor for retracting said at least
one abutment from said rest position, and, a mechanical latch
sensitive to the speed of rotation of said shaft for latching said
at least one abutment in a retracted position against the action of
said resilient component when the rotational speed of said shaft
exceeds a predetermined value, said mechanical latch co-operating
said at least one abutment in such a manner that when said latch
latches said at least one abutment in said retracted position said
at least one abutment must be retracted beyond said latched
position and the speed of rotation of the shaft must be below said
predetermined value in order for said latch to cease to be
operative so that said at least one abutment can move to its rest
position.
6. A thrust reverser actuator lock mechanism comprising a rotatable
shaft, rotation of which in one direction from a rest position
drives an associated thrust reverser from a stowed position towards
an operative position in use, at least one retractable abutment
having a rest position abutting an element rotatable with the shaft
to prevent rotation of the shaft, at least one resilient component
urging said at least one abutment to said rest position, an
hydraulically actuated retractor for retracting said at least one
abutment from said rest position, and, a mechanical latch sensitive
to the speed of rotation of said shaft for latching said at least
one abutment in a retracted position against the action of said
resilient component when the rotational speed of said shaft exceeds
a predetermined value, said mechanical latch co-operating said at
least one abutment in such a manner that when said latch latches
said at least one abutment in said retracted position said at least
one abutment must be retracted beyond said latched position and the
speed of rotation of the shaft must be below said predetermined
value in order for said latch to cease to be operative so that said
at least one abutment can move to its rest position.
7. A thrust reverser actuator lock mechanism as claimed in claim 1
wherein said latch mechanism is a centrifugal mechanism.
8. A thrust reverser actuator lock mechanism as claimed in claim 7
wherein said shaft and said centrifugal mechanism extend within a
sleeve movable axially relative to said shaft to retract said
abutment means.
9. A thrust reverser actuator lock mechanism as claimed in claim 8
wherein said centrifugal mechanism coacts with said sleeve to latch
said sleeve in said retracted position.
10. A thrust reverser actuator lock mechanism as claimed in claim 7
wherein said latch mechanism includes at least one bell-crank lever
pivotally mounted on said shaft, one limb of said lever swinging
radially outwardly of said shaft as said shaft rotates.
11. A thrust reverser actuator lock mechanism as claimed in claim
10 wherein the other limb of said lever is received in a radial
recess in said shaft.
12. A thrust reverser actuator lock mechanism as claimed in claim
11 wherein at least one further bell-crank lever is provided
angularly spaced from the first mentioned lever about the axis of
said shaft.
13. A thrust reverser actuator lock mechanism as claimed in claim
12 wherein said shaft houses resilient means acting on said other
limb of each bell-crank lever to oppose movement of said lever
under centrifugal force.
14. A thrust reverser actuator lock mechanism as claimed in claim
12 wherein the free end region of said one limb of each bell-crank
lever coacts with said sleeve in its retracted position when the
rotational speed of said shaft has exceeded a predetermined value,
to latch said sleeve in its retracted position.
15. A thrust reverser actuator lock mechanism as claimed in claim
14 wherein said sleeve carries an annular bearing encircling said
shaft and each bell-crank lever engages the inner race of said
bearing to latch the sleeve in its retracted position.
16. A thrust reverser actuator lock mechanism as claimed in claim
15 wherein a generally radially outwardly extending shoulder of the
or each bell-crank lever is engageable with a corresponding radial
surface at the end of said inner race and said shoulder and/or said
surface are undercut so that under the action of said resilient
means urging the abutment means to said rest position a self
locking action is generated at said shoulder and said surface
resisting return of the or each bell-crank lever under the action
of said resilient means acting of the or each bell-crank lever.
17. A thrust reverser actuator lock mechanism as claimed in claim 7
wherein in the inoperative position of said centrifugal mechanism a
radial clearance exists between the inner surface of said sleeve
and said mechanism to permit free axial movement of the sleeve
relative to said shaft.
18. A thrust reverser actuator lock mechanism as claimed in claim 7
wherein said sleeve is the movable armature of an
electromagnet.
19. A thrust reverser actuator lock mechanism as claimed in claim 7
wherein said sleeve is a movable piston of an hydraulic
actuator.
20. A thrust reverser actuator lock mechanism comprising a
rotatable shaft, rotation of which in one direction from a rest
position drives an associated thrust reverser from a stowed
position towards an operative position in use, at least one
retractable abutment having a rest position abutting an element
rotatable with the shaft to prevent rotation of the shaft, at least
one resilient component urging said at least one abutment to said
rest position, an electromagnetically actuated retractor for
retracting said at least one abutment from said rest position, and,
a mechanical latch sensitive to the speed of rotation of said shaft
for latching said at least one abutment in a retracted position
against the action of said resilient component when the rotational
speed of said shaft exceeds a predetermined value, said mechanical
latch co-operating with said at least one abutment in such a manner
that when said latch latches said at least one abutment in said
retracted position said at least one abutment must be retracted
beyond said latched position and the speed of rotation of the shaft
must be below said predetermined value in order for said latch to
cease to be operative so that said at least one abutment can move
to its rest position, said mechanical latch including at least two
bell-crank levers pivotally mounted to said shaft and spring urged
to a rest position by spring means housed within said shaft and
from which they swing radially outwardly under centrifugal force as
said shaft exceeds a predetermined rotational speed, and a sleeve
member movable from an axial rest position axially along the axis
of said shaft to retract said abutment means, said bell-crank
levers being engageable with an axial end surface of said sleeve
member when swung radially, outwardly to latch said sleeve member
to hold said abutment means in said retracted position.
21. A thrust reverser actuator lock mechanism comprising a
rotatable shaft, rotation of which in one direction from a rest
position drives an associated thrust reverser from a stowed
position towards an operative position in use, at least one
retractable abutment having a rest position abutting an element
rotatable with the shaft to prevent rotation of the shaft, at least
one resilient component urging said at least one abutment to said
rest position, an hydraulically actuated retractor for retracting
said at least one abutment from said rest position, and, a
mechanical latch sensitive to the speed of rotation of said shaft
for latching said at least one abutment in a retracted position
against the action of said resilient component when the rotational
speed of said shaft exceeds a predetermined value, said mechanical
latch co-operating with said at least one abutment in such a manner
that when said latch latches said at least one abutment in said
retracted position said at least one abutment must be retracted
beyond said latched position and the speed of rotation of the shaft
must be below said predetermined value in order for said latch to
cease to be operative so that said at least one abutment can move
to its rest position said mechanical latch including at least two
bell-crank levers pivotally mounted to said shaft and spring urged
to a rest position by spring means housed within said shaft and
from which they swing radially outwardly under centrifugal force as
said shaft exceeds a predetermined rotational speed, and a sleeve
member movable from an axial rest position axially along the axis
of said shaft to retract said abutment means, said bell-crank
levers being engageable with an axial end surface of said sleeve
member when swung radially, outwardly to latch said sleeve member
to hold said abutment means in said retracted position.
Description
This invention relates to a lock mechanism for an aircraft engine
thrust reverser, particularly a lock mechanism which can form part
of the drive train of a thrust reverser actuator.
An aircraft engine's thrust reverser must only be deployed when the
aircraft has landed. In order to avoid premature or other
inadvertent deployment of the thrust reverser a locking system is
provided for locking the thrust reverser cowl or other thrust
reverser element in a stowed position. Part of the locking system
can be a lock which prevents operation of the thrust reverser
actuating mechanism. Our U.S. Pat. No. 6,138,449 discloses an
hydraulically operated lock mechanism for locking an aircraft
engine thrust reverser actuating mechanism against operation. The
lock mechanism of FIG. 1 of U.S. Pat. No. 6,138,449 has, as shown
in FIGS. 1 and 2 hereto, a shaft 12 which, in order to operate the
thrust reverser actuating mechanism, is rotated at speeds up to
6,000 revolutions per minute by a prime mover, which, in the case
of the mechanism illustrated in U.S. Pat. No. 6,138,449, will be an
hydraulic motor. The shaft 12 can be locked against movement by
first and second pins 15 which are spring urged to a position in
which they obstruct the path of rotation of a plurality of radial
arms 14 carried by the shaft 12. When it is safe and appropriate to
actuate the thrust reverser mechanism of the engine the pins 15 are
retracted hydraulically so that they do not obstruct the arms 14
and the shaft 12 can thus rotate.
A potential problem of the mechanism described in U.S. Pat. No.
6,138,449, but which is extremely unlikely to arise in use, is that
if the hydraulic supply to the retraction mechanism of the pins 15
fails then the pins 15 can be driven forward at a time when the
shaft 12 is rotating at up to 6,000 revolutions per minute. If this
happens then firstly there is a risk that the pins and/or the arms
14 will be irreparably damaged, and secondly there is a possibility
that the shaft 12 will be arrested during rotation while deploying
or stowing the thrust reverser mechanism. The possibility of such
an interruption in the hydraulic supply to the retraction mechanism
of the pins 15 is extremely remote.
There is currently a requirement for electrically operated thrust
reverser systems, and accordingly for electrically operated locking
mechanism associated with such thrust reverser systems. It is a
requirement of the lock mechanism that it is operable to lock the
thrust reverser in a stowed position until released by an
electrical signal, and thereafter, irrespective of interruption of
the electrical energisation, the locking mechanism must not be
rendered operative unless the thrust reverser mechanism has been
returned to its fully stowed condition. It will be recognised that
in order to produce an electrically operated version of the lock
mechanism illustrated in U.S. Pat. No. 6,138,449 it would be
possible, at least in theory, to replace the hydraulic retraction
mechanism of the pins 15 by an electromagnetic retraction
mechanism. However, in the theoretical electrical version of the
arrangement illustrated in 6,138,449 it is recognised that the risk
of inadvertent momentary interruption of an electrical supply to an
electromagnetic retraction mechanism is somewhat greater than the
risk of a dangerous interruption in the hydraulic supply. In
solving this difficulty the inventors have produced an arrangement
which is suitable for use with electrical or hydraulic operation
and accordingly it is an object of the present invention to provide
a lock mechanism for a thrust reverser which cannot be actuated by
inadvertent interruption of the supply of either electrical or
hydraulic power.
In accordance with the present invention there is provided a thrust
reverser actuator lock mechanism comprising a rotatable shaft,
rotation of which in one direction from a rest position drives an
associated thrust reverser from a stowed position towards an
operative position in use, retractable abutment means having a rest
position abutting an element rotatable with the shaft to prevent
rotation of the shaft, resilient means urging said abutment means
to said rest position, and, mechanical latch means sensitive to the
speed of rotation of said shaft for latching said abutment means in
a retracted position against the action of said resilient means
when the rotational speed of said shaft exceeds a predetermined
value.
Preferably said mechanical latch means co-operate with said
abutment means in such a manner that when said latch means latches
said abutment means in said retracted position the abutment means
must be retracted beyond said latched position and the speed of
rotation of the shaft must be below said predetermined value in
order for the latch means to cease to be operative so that the
abutment means can move to its rest position.
Conveniently the mechanism includes electromagnetic retraction
means for retracting said abutment means from said rest
position.
Alternatively said retraction means is hydraulically actuated.
Desirably said latch mechanism is a centrifugal mechanism.
Conveniently said centrifugal mechanism extends within a sleeve
movable axially relative to said shaft to retract said abutment
means.
Preferably said centrifugal mechanism coacts with said sleeve to
latch said sleeve in said retracted position.
Preferably said latch mechanism includes at least one bell-crank
lever pivotally mounted on said shaft, one limb of said lever
swinging radially outwardly of said shaft as said shaft
rotates.
Desirably the other limb of said lever is received in a radial
recess in said shaft.
Conveniently at least one further bell-crank lever is provided
angularly spaced from the first mentioned lever about the axis of
said shaft.
Preferably said shaft houses resilient means acting on the or each
bell-crank lever to oppose movement of said lever under centrifugal
force.
Desirably the free end region of said one limb of the or each
bell-crank lever coacts with said sleeve in its retracted position
when the rotational speed of said shaft has exceeded a
predetermined value, to latch said sleeve in its retracted
position.
Conveniently said sleeve carries an annular bearing encircling said
shaft and the or each bell-crank lever engages the inner race of
said bearing to latch the sleeve in its retracted position.
Preferably a generally radially outwardly extending shoulder of the
or each bell-crank lever is engageable with a corresponding radial
surface at the end of said inner race and shoulder and/or said
surface are undercut so that under the action of said resilient
means urging the abutment means to said rest position a self
locking action is generated at said shoulder and said surface
resisting return of the or each bell-crank lever under the action
of said resilient means acting on the or each bell-crank lever.
Desirably in the inoperative position of said centrifugal mechanism
a radial clearance exists between the inner surface of said sleeve
and said mechanism to permit free axial movement of the sleeve
relative to said shaft.
Conveniently said sleeve is the movable armature of an
electromagnet.
Alternatively said sleeve is a movable piston of an hydraulic
actuator.
In the accompanying drawings:
FIGS. 1 and 2 illustrate a known thrust reverser actuator lock
mechanism of the kind disclosed in U.S. Pat. No. 6,138,449;
FIG. 3 is a diagrammatic cross-sectional view of a thrust reverser
actuator lock mechanism in accordance with one example of the
present invention;
FIGS. 4 and 5 are diagrammatic representations, to an enlarged
scale, of part of the mechanism of FIG. 3; and
FIG. 6 is a view similar to FIG. 3 of a mechanism in accordance
with a second example of the present invention.
Referring to FIGS. 3, 4 and 5 of the drawings, the lock mechanism
includes an elongate, fixed housing 11 rotatably supporting an
elongate shaft 12 in ball bearing assemblies 13a, 13b. At one end
12a the shaft 12 is adapted to be drivingly connected to an
electric motor or other prime mover for powering the engine thrust
reverser mechanism, and at its opposite end 12b the shaft 12 is
adapted for driving connection with a thrust reverser actuator, for
example a ball screw actuator. The bearings 13 provide a very low
friction mounting of the shaft 12 in the fixed housing 11.
Adjacent the bearing 13a the shaft 12 is integrally formed with
three equiangularly spaced, radially outwardly extending arms 14
which thus rotate with the shaft 12. First and second locking pins
15 are disposed diametrically opposite one another on opposite
sides of the axis of the shaft 12 and are slidably received in
appropriate mountings in the housing 11. The pins 15 have a
forward, rest position in which they intersect the rotational path
of the outer end regions of the arms 14. Thus in their rest
positions the pins 15 extend between the arms 14 and one of the
arms 14 will abut one of the pins 15 if an attempt is made to
rotate the shaft 12. The pins thus lock the shaft 12 against
rotation relative to the housing 11 when the pins are in their rest
positions.
Each of the pins 15 includes a blind, axial bore extending into the
pin from the rearward end of the pin, and each bore receives a
respective helically wound compression spring 16 acting between the
housing 11 and the pin 15 to urge the pin to its forward, rest
position (the position illustrated in FIG. 1).
Slidably received within the housing 11 and coaxially receiving the
shaft 12 within it is an elongate hollow sleeve 21 defining an
hydraulically movable piston. A helically wound compression spring
22 is received within the sleeve 21 and acts between an internal
shoulder 23a of the sleeve and an abutment flange 23b fixed to the
housing 11 to urge the sleeve 21 to the left in the drawings to a
rest position in which the forward end of the sleeve 21 abuts part
of the housing 11 slidably receiving the pins 15 (as depicted in
FIG. 1).
At its forward end, remote from the end 12b of the shaft 12 the
sleeve 21 has a radially outwardly extending flange 24 positioned
in front of corresponding radially inwardly extending flanges 25 of
the pins 15. It will be recognised therefore that the sleeve 21 is
moved from its rest position against the spring 22, the flange 24
abutting the flanges 25 ensures that the pins 15 are retracted
against their compression springs 16.
The shaft 12 is formed with an axially extending bore 26 slidably
receiving a plunger 27. A compression spring 28 is received within
the bore 26 and acts between an abutment 29 in the bore and the
plunger 27 to urge the plunger 27 towards the end 12b of the shaft.
The bore 26 is intersected by a transverse bore 31 receiving first
and second bell-crank levers 32, 33. Each of the levers 32, 33 is
pivotally connected to the shaft 12 adjacent the intersection of
the limbs of the lever and thus each lever 32, 33 includes a first
limb extending radially inwardly of the bore 31, and a second limb
which extends axially along the outer surface of the shaft 12 in a
forward direction. The innermost ends of the first limbs of the
levers 32, 33 are rounded and overlap one another, both rounded
ends abutting the end of the plunger 27. It will be recognised that
the plunger 27, being urged by the spring 28 to move towards the
right (as drawn) abuts the first limbs of both of the levers 32, 33
and thus urges the levers 32, 33 to pivot in a direction to press
their second limbs against the outer surface of the shaft 12.
The second limb of each of the levers 32, 33 is elongate, and is
formed at its free end with a head region 32a, 33a, having an
outwardly extending undercut shoulder 34. The second limbs of the
levers 32, 33 extend between the outer surface of the shaft 12 and
the inner surface of the sleeve 21. There is clearance, in the rest
position of the levers 32, 33, between the first limbs of the
levers and the inner surface of the sleeve 21. Moreover, in the
rest position of the sleeve 21 the free ends of the heads 32a, 33a
of the levers protrude beyond the end of the sleeve 21, but the
under-cut shoulders 34 of the levers lie within the confines of the
sleeve 21.
At its forward end the sleeve 21 receives a ball bearing assembly
including an outer race 35 which is secured to the inner surface of
the sleeve 21, and an inner race 36 through which the first limbs
of the levers 32, 33 extend. In the rest position of all of the
components (as illustrated in FIG. 1) the heads 32a, 33a of the
levers 32, 33 do not engage the inner surface of the inner race 36
as a small clearance (not shown) is provided.
An annular collar 37 is received within the housing 11 and is
rigidly secured thereto to define the reaction point against which
the springs 16 of the pins 15 abut. At its inner periphery the
collar 37 defines a hollow cylindrical support tube 38 within which
a region of the sleeve 21 is slidably received. An annular seal 39
is provided in an annular groove in the sleeve 21 and makes sliding
contact with the inner cylindrical surface of the collar 37.
The housing 11 is shaped to define first and second radially
extending, axially spaced hydraulic pressure unions 41, 42 by way
of which hydraulic fluid under pressure can be admitted to the
interior of the housing. The union 41 communicates with an annular
chamber 43 defined between the outer cylindrical surface of the
sleeve 21, the inner cylindrical surface of the housing 11, and
bounded at one end by the tube 38 of the collar 37 and at the
opposite end by a radially extending shoulder 44 on the sleeve 21.
The seal 39 prevents leakage along the interface of the sleeve and
the collar in one direction, and a similar seal 45 received in a
circumferential groove of the sleeve 21 and in sliding engagement
with the inner surface of the housing 11 seals the interface of the
sleeve 21 and the housing 11 in the opposite axial direction.
The union 42 communicates with a second annular chamber 46 defined
between the outer surface of the sleeve 21 and the inner surface of
the housing 11 and bounded at one end by a radially inwardly
extending shoulder 47 of the housing and at the opposite end by a
radially outwardly extending shoulder 48 of the sleeve 21. The seal
45 seals the sliding interface between the sleeve 21 and the
housing 11 in one direction, and a similar seal 49 seals the
sliding interface in the opposite direction. It will be recognised
that hydraulic fluid under pressure admitted to the chamber 43 by
way of the union 41 acts on the shoulder 44 to urge the sleeve 21
to slide from its rest position against the action of the spring
22. Similarly it will be recognised that the application of
hydraulic fluid under pressure to the chamber 46, by virtue of the
fluid acting against the shoulder 48, urges the sleeve 21 to move
to the left in the drawing assisting the action of the spring
22.
In use the hydraulic operating circuit associated with the lock
mechanism includes a high pressure line and a low pressure (drain)
line. The union 42 is permanently connected to the drain line, and
a change-over valve determines whether the union 41 is connected to
the high pressure line or the drain line. The pressure in the high
pressure line is sufficient, when acting against the shoulder 44 of
the sleeve 21, to drive the sleeve 21 against the action of the
spring 22 and the springs 16 to move the sleeve 21 and the pins 15
to the right in the drawings until the flanges 25 of the pins 15
abut the collar 37.
The operation of the lock mechanism is as follows. With the parts
in their rest positions as shown in FIG. 1, if an attempt is made
to rotate the shaft 12 then one of the arms 14 will abut one of the
pins 15 to prevent such rotation. In order to free the shaft for
rotation the change-over valve is operated (usually electrically)
to admit high pressure hydraulic fluid to the chamber 43 and thus
to retract the sleeve 21 against the spring 22 and simultaneously
retracting the pins 15 against their return springs 16 so moving
the pins 15 out of the orbit of the arms 14 and freeing the shaft
12 for rotation. Retraction of the sleeve 21 to the fullest extent
permitted by the flanges 25 of the pins 15 abutting the collar 37
of the housing 11, carries the bearing assembly, and in particular
the inner race 36 of the bearing assembly, axially beyond the
under-cut shoulders 34 of the heads 32a, 33a of the levers.
Accordingly, as the shaft 12 rotates carrying the levers 32, 33
with it, the heads 32a, 33a of the levers can to move radially
outwardly under centrifugal force, pivoting the levers 32, 33
relative to the shaft 12 in a direction to displace the plunger 27
against the action of its return spring 28. Thus the heads 32a, 33a
assume a position in which the shoulders 34 overlie the axial end
surface of the race 36 and should the levers 32, 33 actually engage
the race 36 this will not matter since the inner race 36 can rotate
with the shaft 12 relative to the outer race 35 which is anchored
to the sleeve 21.
Provided that the pressure in the chamber 43 is maintained then the
pivoting movement of the levers 32, 33 against the action of the
spring 28 is irrelevant since the sleeve 21 and pins 15 will be
retained in the fully retracted position. However, if the pressure
supply to the chamber 43 is interrupted while the shaft 12 is
rotating then the sleeve 21 and pins 15 will be returned towards
their rest positions by their return springs. However, only a small
movement of the sleeve and the pins towards their rest positions
will occur before the axial end of the race 36 abuts the shoulders
34 of the levers 32, 33 and further return movement of the pins and
the sleeve is arrested. Thus failure in the pressure supply while
the shaft 12 is rotating does not result in damage to the pins 15
and arms 14 and does not result in rotation of the shaft 12 being
arrested.
It will be recalled that the shoulders 34 of the heads of the
levers 32, 33 are not radial, but are under-cut. The axial end
surface 36a of the race 36 is disposed parallel to the shoulders 34
so that the latching of the sleeve 21 and pins 15 in a retracted
position by the levers 32, 33 is self-locking. Specifically, the
force of the return springs 16, 22 of the pins 15 and the sleeve 21
urging the inclined axial end 37 of the race 36 against the
inclined shoulder 34 of each lever is sufficient to retain each
lever in its outward position against the action of the spring 28
even in the event that the shaft 12 comes to rest, and there is no
centrifugal force urging the heads 32a, 33a of the levers
outwardly. In order to release the latching action of the levers it
is necessary for both the shaft 12 to have ceased or virtually
ceased rotation, and for the chamber 43 to have been pressurised at
least momentarily to move the sleeve 21 to retract the race 36 away
from the shoulders 34 thereby permitting the levers 32, 33 to be
pivoted back to their rest positions by the spring 28. Thereafter
de-pressurisation of the chamber 43 will restore the sleeve 21 and
pins 15 to their rest positions since the shoulders 34 will no
longer be in the path of movement of the inner race 36.
It will be recognised that at very low rotational speeds of the
shaft 12 the levers 32, 33 will not have been pivoted under
centrifugal action to latch the sleeve in a retracted position.
Thus should the chamber 43 be de-pressurised the sleeve 21 and the
pins 15 can be returned to their rest positions. However, the
loading imposed by the spring 28 is calculated to be such that the
rotational speed of the shaft at which the levers can pivot
outwardly under centrifugal force is so low that restoring the pins
15 to their rest positions obstructing the rotational movement of
the shaft 12 will not result in damage.
The normal operation of the lock mechanism is that the chamber 43
will be maintained pressurised until the shaft 12 is stationary in
its rest position, that is to say with the associated thrust
reverser fully stowed. If the chamber 43 has been maintained
pressurised through the whole of the operation then the levers 32,
33 will return to their rest positions under the action of the
spring 28 without ever having acted upon the sleeve 21, and
de-pressurisation of the chamber 43 at that point will allow the
sleeve 21 and the pins 15 to return to their rest positions so that
the shaft 12 is thereafter locked against further rotation until
the chamber 43 is next pressurised.
As mentioned above the change-over valve will connect the chamber
43 either to the high pressure line or to the drain line. It is
important that the chamber 43 is connected to the drain line when
it is not intended that the chamber 43 shall be pressurised since
such a connection will allow hydraulic fluid to drain from the
chamber 43 as the sleeve 21 is moved towards its rest position
under the action of the spring 22. However, it is recognised that
the drain line may also serve other hydraulic actuators associated
with the aircraft. It is known that discharge of high pressure
fluid into the drain line, from elsewhere in the hydraulic system
of the aircraft, can give rise to a transient high pressure pulse
in the drain line. Clearly it is extremely undesirable that such a
transient and spurious high pressure pulse should cause movement of
the sleeve 21 against the action of the spring 22 since this would
retract the locking pins 15 and permit rotation of the shaft 12. If
such a spurious pulse coincided with an unintentional rotation of
the shaft 12 the locking mechanism could become latched in its
inoperative position unintentionally. The provision of the chamber
46 permanently connected to the drain line overcomes this problem.
Specifically, the effective area of the shoulder 48 of the sleeve
21 is equal to the effective area of the shoulder 41 of the sleeve
21, but of coarse is oppositely presented. Thus if, when the
change-over valve connects the chamber 43 to the drain line, there
is a transient high pressure pulse in the drain line, then that
pulse will be presented simultaneously to the shoulders 44 and 48
of the sleeve 21 with the result that the next effect of the pulse
on the sleeve 21 is zero and the sleeve 21 thus remains in its rest
position under the action of the spring 22. Naturally the union 42
and the chamber 46 could be dispensed with if, when the chamber 43
is not intended to be connected to the high pressure line, the
change-over valve connects the chamber 43 to a dedicated drain line
which can be guaranteed to be free of transient pressure
pulses.
The embodiment illustrated in FIG. 6 is operated electrically
rather than hydraulically but its operating principles are similar
to those described above in relation to FIGS. 3 to 5. In place of
the hydraulic actuation system of FIGS. 3 to 5, FIG. 6 illustrates,
secured within the housing 11 at its end remote from the pins 15,
and encircling the shaft 12, a hollow, cylindrical, electromagnet
assembly 17. The assembly 17 includes a hollow cylindrical
electromagnet winding 18 partly enclosed in a ferro-magnetic yoke
including a hollow cylindrical pole piece 19 extending within the
winding 18 from the rearward end of the assembly 17 adjacent the
bearing 13b forwardly towards the bearing 13a. The electromagnet
assembly 17 further includes a ferro-magnetic sleeve defining the
electromagnet armature or plunger 21. The armature 21 is coaxial
with the shaft 12, and extends into the winding 18 from the front
end thereof toward the free end of the pole piece 19. The armature
21 is mounted for axial sliding movement towards and away from the
pole piece 19 and a compression spring 22 urges the armature 21
away from the pole piece 19 to a rest position in which its end
remote from the pole piece 19 abuts the part of the housing 11
supporting the pins 15. An air gap 23 is defined between the
armature and the pole piece in the rest position of the armature.
It will be recognised that energisation of the winding 18 produces
a magnetic flux flow across the air gap 23 whereby the armature 21
is magnetically attracted towards the pole piece 19 against the
action of the spring 22.
At its forward end, remote from the pole piece 19, the armature 21
has a radially outwardly extending flange 24 positioned in front of
corresponding radially inwardly extending flanges 25 of the pins
15. It will be recognised therefore than when the armature 21 is
moved to close the air gap 23 the flange 24 abutting the flanges 25
ensures that the pins 15 are retracted against their compression
springs by the movement of the armature 21 to close the air gap
23.
As described above, the shaft 12 is formed with an axially
extending bore 26 slidably receiving a plunger 27. A compression
spring 28 is received within the bore 26 and acts between an
abutment 29 in the bore and the plunger 27 to urge the plunger 27
towards the end 12b of the shaft. The bore 26 is intersected by a
transverse bore 31 receiving first and second bell-crank levers 32,
33. Each of the levers 32, 33 is pivotally connected to the shaft
12 adjacent the intersection of the limbs of the lever and thus
each lever 32, 33 includes a first limb extending radially inwardly
of the bore 31, and a second limb which extends axially along the
outer surface of the shaft 12 in a forward direction. The innermost
ends of the first limbs of the levers 32, 33 are rounded and
overlap one another, both rounded ends abutting the end of the
plunger 27. It will be recognised that the plunger 27, being urged
by the spring 28 to move towards the right (as drawn) abuts the
first limbs of both of the levers 32, 33 and thus urges the levers
32, 33 to pivot in a direction to press their second limbs against
the outer surface of the shaft 12.
The second limb of each of the levers 32, 33 is elongate, and is
formed at its free end with a head region 32a, 33a, having an
outwardly extending under-cut shoulder 34. The second limbs of the
levers 32, 33 extend between the outer surface of the shaft 12 and
the inner surface of the armature 21. There is clearance, in the
rest position of the levers 32, 33, between the first limbs of the
levers and the inner surface of the armature 21. Moreover, in the
rest position of the armature 21 the free ends of the heads 32a,
33a of the levers protrude beyond the end of the armature 21, but
the under-cut shoulders 34 of the levers lie within the confines of
the armature 21.
At its forward end the armature 21 receives a ball bearing assembly
including an outer race 35 which is secured to the inner surface of
the armature 21, and an inner race 36 through which the first limbs
of the levers 32, 33 extend. In the rest position of all of the
components (as illustrated in FIG. 1) the heads 32a, 33a of the
levers 32, 33 do not engage the inner surface of the inner race 36
as a small clearance (not shown) is provided.
The operation of the lock mechanism is as follows. With the parts
in their rest position as shown in FIG. 1, if an attempt is made to
rotate the shaft 12 then one of the arms 14 will abut one of the
pins 15 to prevent such rotation. In order to free the shaft for
rotation the winding 18 is energised thus retracting the armature
21 against the spring 22 and simultaneously retracting the pins
against their return springs so moving the pins 15 out of the orbit
of the arms 14 and freeing the shaft 12 for rotation. Retraction of
the armature 21 to the fullest extent permitted either by closure
of the air gap 23 or by the rear ends of the pins 15 abutting an
internal wall of the housing 11, carries the bearing assembly, and
in particular the inner race 36 of the bearing assembly, axially
beyond the under-cut shoulders 34 of the heads 32a, 33a of the
levers. Accordingly, as the shaft 12 rotates carrying the levers
32, 33 with it, the heads 32a, 33a of the levers tend to move
radially outwardly under centrifugal force, pivoting the levers 32,
33 relative to the shaft 12 in a direction to displace the plunger
27 against the action of its return spring 28. Thus the heads 32a,
33a assume a position in which the shoulders 34 overlie the axial
end surface of the race 36 and should the levers 32, 33 actually
engage the race 36 this will not matter since the inner race 36 can
rotate with the shaft 12 relative to the outer race 35 which is
anchored to the armature 21.
Providing that the winding 18 is maintained energised then the
pivoting movement of the levers 32, 33 against the action of the
spring 28 is irrelevant since the armature 21 and pins 15 will be
retained in the fully retracted position. However, if the power
supply to the winding 18 is interrupted while the shaft 12 is
rotating then the armature 21 and pins 15 will be returned towards
their rest positions by their return springs. However, only a small
movement of the armature and the pins towards their rest positions
will occur before the axial end of the race 36 abuts the shoulders
34 of the levers 32, 33 and further return movement of the pins and
the armature is arrested. Thus failure in the energisation of the
winding 18 while the shaft 12 is rotating does not result in damage
to the pins 15 and arms 14 and does not result in rotation of the
shaft 12 being arrested.
It will be recalled that the shoulders 34 of the heads of the
levers 32, 33 are not radial, but are under-cut. The axial end
surface 37 of the race 36 is disposed parallel to the shoulders 34
so that the latching of the armature 21 and pins 15 in a retracted
position by the levers 32, 33 is self-locking. Specifically, the
force of the return springs of the pins 15 and the armature 21
urging the inclined axial end 37 of the race 36 against the
inclined shoulder 34 of each lever is sufficient to retain each
lever in its outward position against the action of the spring 28
even in the event that the shaft 12 comes to rest, and there is no
centrifugal force urging the heads 32a, 33a of the levers
outwardly. In order to release the latching action of the levers it
is necessary for both the shaft 12 to have ceased or virtually
ceased rotation, and for the winding 18 to have been energised at
least momentarily to retract the race 36 away from the shoulders 34
thereby permitting the levers 32, 33 to be pivoted back to their
rest positions by the spring 28. Thereafter de-energisation of the
winding 18 will restore the armature 21 and pins 15 to their rest
positions since the shoulders 34 will no longer be in the path of
movement of the inner race 36.
It will be recognised that at very low rotational speeds of the
shaft 12 the levers 32, 33 will not have been pivoted under
centrifugal action to latch the armature in a retracted position.
Thus should the winding 18 be de-energised the armature 21 and the
pins 15 can be returned to their rest positions. However, the
loading imposed by the spring 28 is calculated to be such that the
rotational speed of the shaft at which the levers can pivot
outwardly under centrifugal force is so low that restoring the pins
15 to their rest positions obstructing the rotational movement of
the shaft 12 will not result in damage.
The normal operation of the lock mechanism is that the winding 18
will be maintained energised until the shaft 12 is stationary in
its rest position, that is to say with the associated thrust
reverser fully stowed. If the winding 18 has been maintained
energised through the whole of the operation then the levers 32, 33
will return to their rest positions under the action of the spring
28 without ever having acted upon the armature 21, and
de-energisation of the winding 18 at that point will allow the
armature 21 and the pins 15 to return to their rest positions so
that the shaft 12 is thereafter locked against further rotation
until the winding 18 is next energised.
* * * * *